Looking for patterns, I noticed that the last digit of each number was in descending order (0, 9, 8, 7, 6...)Looking at the remainder of each number, I noticed that they had a pattern as well. If the last digit of the number is x, then the first part of the number cycles through x-2, x+2, 2x+2. The only exceptions are where x-2 would fall below 1, in which case they seem to just use 1 instead.